Abstract

Low molecular weight polyether (PE) or polyester polyols can produce novel elastomeric urethane products when cured with diisocyanate which are then utilized for formation of castable energetic composites in addition to many more applications. In this work four different kinds of diisocyanates, isophorone diisocyanate (IPDI), methylenediphenyl diisocyanate (MDI), 2,2,4-trimethyl hexamethylene diisocyanate (TMDI), and toluene diisocyanate (TDI), were used to react with a PE to form PE-based polyurethanes (PUs); they were denoted PE/IPDI, PE/MDI, PE/TMDI, and PE/TDI, respectively. The effect of the four diisocyanate groups in the PE-based PUs on the thermal degradation behavior, thermal degradation kinetics, reaction model, and thermodynamic parameters of the PE/IPDI, PE/MDI, PE/TMDI, and PE/TDI samples were investigated by thermogravimetric analysis (TGA) and derivative thermal gravimetric analysis (DTGA) methods. On the basis of the degradation peak temperature at a high heating rate, the thermal stability of the PU followed the order PE/TDI > PE/TMDI > PE/MDI > PE/IPDI. The activation energy for the thermal degradation was derived using the Flynn–Wall–Ozawa (FWO) method from the TGA data and the average values of the PE/IPDI, PE/MDI, PE/TMDI, and PE/TDI samples were found to be 136.9, 148.0, 132.3, and 155.7 kJ mol^‒1, each at various conversions from 0.05 to 0.95, respectively. In addition, the results of the activation energies obtained from the Kissinger–Akahira–Sunnse (KAS) method were in good agreement and consistent with those obtained the FWO method. The reaction models of the degradation reaction were investigated through the Coats–Redfern method and all PUs samples were probably best described by the Avarami–Erofeyev (A ₂) and reaction order (F ₁) models. The kinetic and thermodynamic parameters for formation of the activated complex of all PUs, such as the activation energy (E_a ), enthalpy of activation (ΔH ^#), Gibbs free energy of activation (ΔG ^#), and entropy of activation (ΔS ^#), were investigated. The investigated thermal kinetic and thermodynamic parameters indicated that there was significant variation in the properties of the PUs containing the different diisocyanate groups.

摘要

当用二异氰酸酯固化时，低分子量聚醚（PE）或聚酯多元醇可以生产新型的弹性体聚氨酯产品，然后将其用于形成可浇铸的高能复合材料，以及更多的应用。在这项工作中，使用四种不同类型的二异氰酸酯（异佛尔酮二异氰酸酯（IPDI），亚甲基二苯基二异氰酸酯（MDI），2,2,4-三甲基六亚甲基六亚甲基二异氰酸酯（TMDI）和甲苯二异氰酸酯（TDI））与PE反应形成PE基聚氨酯（PU）；它们分别表示为PE / IPDI，PE / MDI，PE / TMDI和PE / TDI。PE基PU中的四个二异氰酸酯基团对PE / IPDI，PE / MDI，PE / TMDI的热降解行为，热降解动力学，反应模型和热力学参数的影响 通过热重分析（TGA）和衍生热重分析（DTGA）方法研究了PE / TDI样品。基于高加热速率下的降解峰值温度，PU的热稳定性遵循PE / TDI> PE / TMDI> PE / MDI> PE / IPDI的顺序。使用Flynn-Wall-Ozawa（FWO）方法从TGA数据中得出了热降解的活化能，发现PE / IPDI，PE / MDI，PE / TMDI和PE / TDI样品的平均值为是136.9、148.0、132.3和155.7 kJ mol^‒1，分别从0.05到0.95的各种转换。此外，从基辛格-阿卡希拉-Sunnse（KAS）方法获得的活化能结果与FWO方法获得的结果相吻合且一致。通过Coats-Redfern方法研究了降解反应的反应模型，所有PU样品可能最好用Avarami-Erofeyev（A ₂）和反应阶数（F ₁）模型来描述。用于形成所有PU的活化复合物的动力学和热力学参数，例如活化能（E _a ），活化焓（ΔH ^＃），活化吉布斯自由能（ΔG ^＃）和活化熵（ΔS ^＃），进行了研究。研究的热动力学和热力学参数表明，包含不同二异氰酸酯基团的聚氨酯的性能存在显着差异。